The study was performed exclusively using a BM-Respirometer from SURCIS, S.L.
This “batch system” respirometer consists of: a single thermostatically controlled vessel, divided into two interconnected compartments with closed recirculation loop between the two. A constant air flow is supplied via a ceramic diffuser in the conditioning compartment, and a combined oxygen/temperature sensor in the reaction compartment controls the DO and temperature. Both compartments are kept completely mixed by means of paddle stirrers and a peristaltic recirculation pump.
The BM-EVO is doted by three different operation modes (Static, Cyclic and Dynamic).
In this study we are only making use of the dynamic R mode for toxicity and biomass yield followed by the COD fractioning and COD removal rate. The R mode is based on the addition of one or several small sample doses in the returned activated sludge previously aerated in the reactor vessel. For R mode the measuring system was previously calibrated to get the corresponding offsets and factors with the purpose to determine the corresponding CO and bCOD results in mg/l units.